TAKOTNA, Alaska (AP)  Aaron Burmeister on Thursday took the lead in the Iditarod Trail Sled Dog Race, and a Norwegian musher had to abandon the race after a sled accident that organizers said probably left him with internal injuries.

Burmeister, a musher from Nenana in his 12th race, was the first out of Ophir, a trail checkpoint 687 miles from the finish in Nome. He was able to take the lead while four-time champion and previous race leader Martin Buser took his mandatory 24-hour layover.

Hugh Neff was next back on the trail from Ophir, followed by two-time defending champion Lance Mackey and 10 other mushers.

Norway's Bjornar Andersen left the race Thursday farther back on the trail in Takotna after his injury the previous day.

The extent of his injuries was not immediately known, race spokesman Chas St. George said. Andersen was taken by a small airplane to McGrath, where he boarded a commercial flight Thursday for Anchorage and additional medical care.

The race began with 67 teams, and three have left. The front-runners are expected to finish next week.

John Anderson, the race judge in Takotna, said he knew something was wrong with Andersen when he arrived in 14th place, well behind where he should have been, given his strong dog team.

Anderson said the musher was examined by a physician at the Takotna checkpoint, who is "pretty sure that he has some internal injuries."

Andersen complained about abdominal pain and decided to leave the competition rather than face an uncertain future on a 150-mile of tough trail ahead after Takotna, Anderson said. The musher's uncle, Robert Sorlie, is a former Iditarod champion.

"He is such a competitor," the race judge said. "He really didn't want to scratch, but he knew it was the right thing to do."

Race marshal Mark Nordman also visited the musher before the decision was made.

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